Blender 2.8 Texture Paint Nodes - supported in Unity?
In general, node logic is specific to Blender and will not be supported in other software. Material and texture creating in far from standardised across technologies, and thus trying to match and support it is just about impossible. In certain cases, certain exporters may detect similar nodes and try and recreate them in the target format/application (for example in the case of fbx export, 2.8 uses the principled shader for basic material settings), however this is the exception, not the rule. 

The solution for exporting generated textures to any other program is to bake them to an image file.